The present invention is directed to a method of removing matrix material from a matrix-enclosed fiber optic cable, and a device for use with the method. More particularly, the present invention pertains to a solvent capture method for removing matrix material from a fiber optic ribbon cable, and a portable, disposable kit for use with the method.
Optical fibers provide a well-known medium for conveying information in data and communications systems, such as computer and telephone networks. The light transmission capability of optical fibers is greatest when the fibers are straight, because they are subject to signal attenuation with bending. Manufacturers typically coat optical fibers, which are made of glass cores surrounded by glass cladding, with at least one layer of protective polymer matrix. This protective matrix shields the glass fibers from damage and reduces unnecessary bending.
Several optical fibers may be laid next to each other in the same plane, substantially parallel to each other, and bonded to each other with a common matrix, usually an acrylic. Such a collection of fibers, generally in the range of 2–24 individual fiber strands, is termed a fiber optic ribbon. Ribbons continue to grow in popularity because they permit increased fiber packing density within a given space. Higher packing densities allow more fibers to be placed in a given diameter cable, more efficiently utilizing existing cable ducts. Because fiber strands within a ribbon frequently are color-coded, ribbons provide easier fiber identification.
Despite the many advantages associated with fiber optic ribbon, difficulties arise when technicians need to expose individual fibers for installation, fiber splicing, repair, or maintenance. To expose individual fibers within a ribbon, technicians must first strip away the matrix surrounding the fibers that secures them to each other. The prior art describes many methods for removing matrix from fiber optic ribbon, including manual, chemical, and adhesive stripping methods, as well as peeling the matrix with a tool.
Manual stripping methods include sanding, cutting, or picking. Sanding necessarily requires the use of an abrasive substance against delicate optical fibers, resulting in the possibility of substantial damage to the fibers. Cutting and picking methods require the use of razor blades, knives, scissors, spatulas, small picks, or even fingernails. In addition to being dangerous to technicians, these methods are very time consuming and frequently cause fiber breakage. See, e.g. “Sheath Removal and Stripping of 8 and 12-Fiber Ribbon Interconnect Cables,” published by Corning Cable Systems, for an example of a cutting and picking method.
Chemical stripping methods have included soaking fiber terminals or mid-spans in either ethyl alcohol or acetone. Acetone is not favored because of its strong odor, and its propensity to chemically attack other cable components. Ethyl alcohol is problematic because it is not effective on most of the ribbon matrix materials currently in use. In addition, chemical solvents used for stripping tend to evaporate or dissipate before they are able to thoroughly dissolve the matrix. One known method for chemically removing ribbon matrix includes the steps of folding three lint-free wipers in half, placing the wipers in a “snack-size” small plastic bag, spraying a solvent into the wipers, and holding a ribbon in the solvent for a set period of time, to allow the matrix to dissolve. Though the plastic bag reduces solvent evaporation, technicians find it cumbersome to have to hold the bag, the solvent container, and the optical fibers all at once. Also, while the plastic bag contains the solvent, easily spilled excess solvent remains loose in the bag, making matrix removal a particularly messy experience.
Fiber optic ribbons may be adhesively stripped by applying adhesive tape or liquid to one side of the ribbon and then laying the ribbon on a peel board, adhesive-side down. When the ribbon is pulled away from the adhesive and peel board, a portion of the matrix remains on the board, thereby exposing individual fibers. A typical example of this method is disclosed in U.S. Pat. No. 5,460,683 to Beasley, Jr. et al. Unfortunately, the adhesive stripping method often creates centerline angles in the fibers, resulting in signal attenuation. Attenuation may be particularly pronounced when the technician pulling the ribbon away from the peel board favors one side or the other, creating an uneven peel force distribution across the width of the ribbon.
Methods of peeling the matrix with tools, such as the lever device designed to be used with a peel board disclosed in U.S. Pat. No. 6,584,258 to Thompson et al., improve upon methods using adhesive alone. However, even a consistently distributed peel force cannot guarantee a reliably uniform peel. In addition, the complex construction of such compound peel tools renders them not easily portable, preventing technicians from using them for field service.
Accordingly, there exists a need for an effective method of removing matrix from fiber optic cables that thoroughly and evenly eliminates matrix without damaging the fibers. Desirably, such a method is entirely portable, useful for both field service and in-plant applications. Such a method desirably employs a chemical solvent to dissolve the matrix. Most desirably, such a method includes use of a folder that stores disposable materials used during practice of the method and provides a work station.